An air conditioning unit is an air conditioning appliance used for directly providing processed air to a closed room, space or area, which is generally referred to as an air conditioner. Split-type heat pump air conditioners that are currently and massively produced and applied use compressors as heat pumps, and the structure thereof is shown in FIG. 1. As shown in FIG. 1, it can be known that the heat pump air conditioner comprises an indoor air conditioner 10, a compressor 11, a first dryer 12, a second dryer 13, a first throttle 14, a second throttle 15, a first one-way valve 16, a second one-way valve 17, a four-way reversing valve 18 and an outdoor air conditioner 19. The indoor air conditioner 10 comprises an evaporator/condenser 101 and a cross-flow blower 102. The outdoor air conditioner 19 comprises a condenser/evaporator 191 and an axial blower 192. The first throttle 14, the first dryer 12, the second dryer 13, and the second throttle 15 are sequentially connected in series. One end of the first throttle 14 away from the first dryer 12 is interconnected with one end of the evaporator/condenser 101. One end of the second throttle 15 away from the second dryer 13 is interconnected with one end of the condenser/evaporator 191. One end of the first one-way valve 16 is interconnected with one end of the first throttle 14 away from the first dryer 12, and another end is interconnected with one end of the first dryer 12 away from the first throttle 14. One end of the second one-way valve 17 is interconnected with one end of the second dryer 13 away from the second throttle 15, and another end is interconnected with one end of the second throttle 15 away from the second dryer 13. The four-way reversing valve 18 comprises four connection ends (1), (2), (3) and (4) The connection ends (1) and (3) are connected with the compressor 11, the connection end (2) is connected with another end of the evaporator/condenser 101, and the connection end (4) is connected with another end of the condenser/evaporator 191. The cross-flow blower 102 is connected between the evaporator/condenser 101 and the connection end (2), and the axial blower 192 is located at one side of the condenser/evaporator 191. The operating principles of the heat pump air conditioner according to the present invention are as follows.
During cooing, the connection ends (1) and (4) of the four-way reversing valve 18 are interconnected with each other, and the connection ends (2) and (3) are interconnected with each other. Low temperature and low pressure refrigerant gas is sucked by the compressor 11, is then compressed to be high pressure and high temperature gas, is then discharged to the condenser/evaporator 191, and is then cooled by cold air discharged from the axial blower 192. By such a process, the high pressure and high temperature gas in the condenser/evaporator 191 is condensed into liquid. The liquid then flows through the second one-way valve 17 to the first dryer 12 and the first throttle 14 and becomes low pressure and low temperature liquid for entering into the evaporator/condenser 101 and then being vaporized. Heat of indoor air sucked due to operation of the axial blower 102 is sucked to cool the indoor air, and the cooled indoor air is returned back to the room via an air passage under the effect of the axial blower 102.
During heating, the connection ends (1) and (2) of the four-way reversing valve 18 are interconnected with each other, and the connection ends (3) and (4) are interconnected with each other. Low temperature and low pressure refrigerant gas is sucked by the compressor 11, is then compressed to be high pressure and high temperature gas, is then discharged to the evaporator/condenser 101, and is then discharged by the axial blower 102 for heating indoor cool air. By such a process, the high pressure and high temperature gas in the evaporator/condenser 101 is condensed into liquid. The liquid then flows through the first one-way valve 16 to the second dryer 13 and the second throttle 15 and becomes low pressure and low temperature liquid for entering into the condenser/evaporator 191 and then being vaporized. The function of the four-way reversing valve 18 is that: when the flow direction of the refrigerant in the system is opposite to the direction during cooling, the condenser/evaporator 191 absorbs heat in the air, and the evaporator/condenser 101 releases the heat to realize heating at an indoor side, such that temperature of the air in the room is increased.
Currently, in our country, the environmental temperature during operation of the heat pump air conditioner is generally between −7° C. to 43° C., and the environmental temperature during operation of the heat pimp air conditioner under a tropical environment can be even −7° C. to 52° C. However, a coefficient of performance of the existing heat pump air conditioner is relatively low during operation at a lower or higher environmental temperature, especially, during low-temperature heating. The compressor has to be shut down when a surface of the evaporator of the outdoor air conditioner is frozen. The compressor can be restarted and operated only when the frost is cleaned, which influences the popularization and use of the heat pump air conditioner in cold areas.
Besides, evaporators and condensers (and the above-mentioned evaporator/condenser 101 and condenser/evaporator 191) sold in the market today use the form of a sleeve structure. That is, an aluminum fin is sleeved on a copper tube, and then a heat dissipation aluminum fin closely rests against the cooper tube through a mechanical expansion tube or a hydraulic expansion tube. The aluminum fin is used to increase a heat exchange area and the heat transfer coefficient at an air side of the heat exchanger, thereby increasing the heat exchange amount of the heat exchanger. However, thermal resistance between this structural type of heat exchanger copper tube and the aluminum fin is larger, and the heat transfer coefficient is low. Moreover, the indoor air conditioner and the outdoor air conditioner are larger in volume and are relatively heavy.